Theoretical design of a magnetic-nozzle acceleration system for fusion propulsion

Numerical simulations of magnetic-nozzle flows have been successfully conducted at The Ohio State University in the interest of providing valuable insights and detailed design guidance to near-future experimental efforts. Quasisteady modeling using helium propellant with classical resistivity demonstrates a neariyisentropic expansion of the confined gas to exhaust speeds that exceed 270km/s. For a stagnation temperature of 100eV, approximately 70% of the thermal power is converted to thrust power (0.4GW) producing 4.6kN of thrust. Further expansion can lead to additional gains in thrust by utilizing the thermal power that is retained in the 20eV-plasma at the exit. In the inlet of the nozzle - near the plasma-field interface - the development of nonuniformities in the magnetic field is exposed. For T₀=100eV, as much as 50% of the mass flux is found to penetrate the current-layer across the magnetic field lines. At fixed plasma pressure and applied field the layer at the throat increases in thickness from approximately 3cm to 5cm when the stagnation temperature is decreased from 250 to 100eV.